1. 1987. Impact of intensive forestry practices on net stand values in British Columbia. B.C. Ministry of Forests FRDA-Report 014. 109 p.

Keywords: release treatments

fertilization

thinning

yield

economics

Abstract: Yield responses to major silvicultural treatments (regeneration method, brushing and weeding, spacing and thinning and fertilizer use) are analysed in relation to growth and yield theory, and their translation into operational use of treatments to increase merchantable vol. is considered. Data from coastal Douglas fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla) and western hemlock/Abies amabilis stands and interior white spruce (Picea glauca), lodgepole pine (Pinus contorta) and wet belt Douglas fir stands are used to quantify the net present value of treatments in terms of improvement in net stand values and merchantable vol. Potentially viable treatment options are identified for each stand type present.

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2. Bailey, J.D. and J.C. Tappeiner. 1998. Effects of thinning on structural development in 40- to 100-year-old Douglas-fir stands in western Oregon. Forest-Ecology-and-Management 108(1/2): 99-113.

Keywords: thinning

commercial thinning

regeneration

tree morphology

Abstract: The composition and structure of the understorey was studied in thinned and unthinned Douglas fir/western hemlock (Pseudotsuga menziesii/Tsuga heterophylla) stands on 32 sites in western Oregon. These stands had regenerated naturally after timber was harvested between 1880 and 1940; they were thinned between 1969 and 1984. Commercially thinned stands had 8-60% of their volume removed 10-24 yr before the study (in 1993-95). Undisturbed old-growth Douglas fir stands were present for comparison on 20 of these paired sites. Conifer regeneration density and frequency were consistently greater in thinned than unthinned stands. For example, average seedling density in thinned stands (1433/ha) was significantly greater than in unthinned stands (233/ha), but very similar to that in old-growth stands (1010/ha). Seedling density and frequency were strongly related to the volume removed and to stand density index (and other measures of overstorey density) just after thinning. In thinned stands, the density of small trees (intermediate crown class overstorey trees and advanced regeneration) was 159/ha, significantly greater than in unthinned stands (90/ha), but not significantly different from that of old-growth (204/ha). The live crown ratio of these trees in thinned stands (66%) was greater than in unthinned (44%) and old-growth (48%) stands. Cover and stem density of shrubs was variable in all 3 stand types. There was significantly less tall shrub cover in unthinned stands than in either thinned or old-growth stands, which did not differ. Thinned stands had the most low shrub cover. Salal (Gaultheria shallon) and bracken fern (Pteridium aquilinum) cover was greater in thinned stands than in the other stand types, but there was no difference in sword fern (Polystichum munitum) and Oregongrape [Berberis nervosa] cover. Leaf area index in thinned stands (6.6) was not significantly different from that in unthinned (6.8) and old-growth stands (7.1); however, there was more leaf area in shrubs in the thinned stands. Thinning young Douglas-fir stands will hasten the development of multistorey stands by recruitment of conifer regeneration in the understorey as well as by enabling the survival of small overstorey trees and growth of advanced understorey regeneration. Thinning will also help develop the shrub layer by increasing tall shrub stem density and cover of some low shrubs.

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3. Barbour, R.J., S. Johnston, J.P. Hayes and G.F. Tucker. 1997. Simulated stand characteristics and wood product yields from Douglas-fir plantations managed for ecosystem objectives. Forest-Ecology-and-Management 91(2/3): 205-219.

Keywords: thinning

yield

wood quality

Abstract: Hundreds of thousands of hectares of Douglas fir (Pseudotsuga menziesii) plantations in coastal forests in the US Pacific Northwest have been established over the past 40 years. Density management regimes designed to increase structural and compositional diversity in these plantations are being tested and implemented on an operational scale, in order to satisfy goals of ecosystem management. These regimes are designed to promote various tree and stand characteristics, such as trees with large limbs, stands with multi-layered canopies, and dense unthinned patches. Changes in forest management policy associated with these types of regimes raise questions about whether it is possible to manage for both ecosystem values and timber production. State-of-the-art growth models were used to simulate stand development and wood product yields under several silvicultural prescriptions. The results indicated that timing and intensity of early thinnings are critical in determining both stand structure and wood quality. It is concluded that it should be possible to manage Douglas fir plantations to provide a high degree of structural diversity, and wood products with a quality similar to that grown in many industrial plantations.

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4. Barbour, R.J. and D.L. Parry. 2001. Log and lumber grades as indicators of wood quality in 20- to 100-year-old Douglas-fir trees from thinned and unthinned stands. Pacific-Northwest-Research-Station,-USDA-Forest-Service General-Technical-Report PNW-GTR-510. 22 p.

Keywords: thinning

commercial thinning

wood quality

Abstract: This report examines the differences in wood characteristics found in coastal Pacific Northwest Douglas-fir (Pseudotsuga mensziesii) trees harvested at the age of 70 to 100 years old or at the age of 40 to 60 years from a trial involving multiple thinnings in Seattle, Washington, USA. Comparisons of differences in domestic log grades suggest that the proportion of log volume in the higher grades (Special Mill and No. 2 Sawmill) increased with both stand age and tree size. Simulation of lumber grade yields based on log characteristics suggests that yields of higher grades of lumber increased until about age 60 to 70, and then levelled off over the rest of the age range examined in this analysis. We included structural lumber products in the analysis but not higher value appearance grade products, and some evidence suggests that yields of these products might have begun to increase in the oldest trees. The analysis also showed that the younger trees had larger branches and more juvenile wood, possibly because they had been grown in stands that received a higher level of early stand management than the older trees. If these young trees were grown to the ages of 70 to 100, they likely would not produce the same log and lumber grade yields found in the older trees we examined.

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5. Barclay, H., H. Brix and C.R. Layton. 1982. Fertilization and thinning effects on a Douglas-fir ecosystem at Shawnigan Lake: 9 year growth response. Pacific-Forestry-Centre, Canadian-Forest-Service Information-Report BC-X-238. 35 p.

Keywords: fertilization

thinning

growth

Abstract: Further results are given for a trial established in 1970 in a 24-yr-old stand in British Columbia, last measured 6 yr after treatment. Volume increments over 9 yr for heavy thinning alone, heavy fertilizer (urea) treatment alone, or both together, were 46%, 75% and 120%, respectively.

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6. Barclay, H.J. and H. Brix. 1984. Effects of urea and ammonium nitrate fertilizer on growth of a young thinned and unthinned Douglas-fir stand. Canadian-Journal-of-Forest-Research 14(6): 952-955.

Keywords: fertilization

thinning

growth

tree physiology

tree/stand health

Abstract: The effects were studied of 2 sources of nitrogen fertilizer applied at rates of 224 and 448 kg/ha N on growth of thinned and unthinned plots established in 1970 in a 24-yr-old stand on southern Vancouver Is., British Columbia. Ammonium nitrate yielded higher growth of diam. and vol. than urea over a 9-yr period, particularly with thinning. Ht. growth was not affected by nitrogen source. The efficiency of nitrogen fertilizing in terms of stem vol. response per kilogram of nitrogen applied was greatest with ammonium nitrate in thinned plots. Tree mortality increased substantially with fertilizing for both sources, and decreased markedly with thinning.

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7. Barclay, H.J. and H. Brix. 1985a. Effects of high levels of fertilization with urea on growth of thinned and unthinned Douglas-fir stands. Canadian-Journal-of-Forest-Research 15(4): 730-733.

Keywords: fertilization

thinning

growth

tree physiology

tree/stand health

Abstract: Diameter height and volume growth were documented for 9 yr after thinning and fertilizing in a 24-yr-old stand on a poor site on southern Vancouver Is. The treatments involved 3 thinning treatments (0, 1/3, and 2/3 b.a. removed) and 6 fertilizer treatments (0-1344 kg/ha N) with urea. Increments for both diameter and gross volume increased with the rate of fertilizer application and responses were still apparent 9 yr after treatment. For unthinned plots, the 9-yr volume growth responses were 30, 50, and 80% with fertilizer rates of 224, 448, and 896 kg/ha N, respectively. The efficiency of fertilizer use, measured as stem volume response per unit of nitrogen applied, decreased with rate of fertilizer application, but this result may change over a longer response period. There was a positive interaction between fertilizing and thinning such that high amounts of both mutually enhanced growth. Mortality increased with fertilizing, but only noticeably in unthinned plots.

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8. Barclay, H.J. and H. Brix. 1985b. Fertilization and thinning effects on a Douglas-fir ecosystem at Shawnigan Lake: 12-year growth response. Pacific-Forestry-Centre, Canadian-Forest-Service Information-Report BC-X-271. 34 p.

Keywords: fertilization

thinning

growth

Abstract: [See FA 45, 2316] Further results are given from the study established in 1970 in a 24-yr-old stand in British Columbia. Fertilizers (urea) and thinning both increased vol. increments over 12 yr. Refertilization 9 yr after initial treatment has produced substantial increases in vol. increment.

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9. Barclay, H.J. and C.R. Layton. 1990. Growth and mortality in managed Douglas fir: relation to a competition index. Forest-Ecology-and-Management 36(2-4): 187-204.

Keywords: fertilization

thinning

growth

tree/stand health

Abstract: Twelve-year increments of diameter at breast height (DBH), height, and volume in thinned and fertilized 45-year-old Douglas fir (Pseudotsuga menziesii) stands on Vancouver Island, Canada, were related (by regression) to degree of thinning, amount of fertilizer (3x3 factorial), initial DBH, and a competitive stress index (CSI). The ability of the CSI to predict growth after treatment was examined. Causes of tree death, and CSI data, are presented, and the relationship between them discussed. The CSI was found to be only moderately good at predicting Douglas fir growth and mortality: initial DBH provided a better predictor. Most mortality in unthinned plots resulted from suppression, and correlated reasonably well with CSI; mortality in thinned plots was not correlated with CSI, and resulted principally from snow damage. Tree height variability generally became less over the 12 years following treatment, which is more consistent with two-sided than one-sided competition predictions, a result which is contrasted to that of many other species.

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10. Barclay, H.J., P.C. Pang and D.F.W. Pollard. 1986. Aboveground biomass distribution within trees and stands in thinned and fertilized Douglas-fir. Canadian-Journal-of-Forest-Research 16(3): 438-442.

Keywords: fertilization

thinning

carbon allocation

Abstract: Nine years after heavy thinning and fertilization with urea, 34-yr-old Douglas firs at Shawnigan Lake (British Columbia) were destructively sampled. Dry wt. of seven aboveground components (wood, bark, dead branches, new or old foliage, new twigs and live branches) were determined and regression equations from d.b.h. were developed. Differences among treatments were shown for all biomass components and for the proportion of the total biomass allocated to each component. Thinning reduced the proportion of wood, bark and dead branches while increasing the proportion of foliage and live branches. Fertilization increased the proportion of branches but had negligible effects on the proportions of other components.

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11. Barclay, H.J. and J.A. Trofymow. 2000. Relationship of readings from the LI-COR canopy analyzer to total one-sided leaf area index and stand structure in immature Douglas-fir. Forest-Ecology-and-Management 132(2/3): 121-126.

Keywords: fertilization

thinning

tree morphology

Abstract: Estimation of leaf area is important in predicting potential growth. This estimation is often done by means of a photometer, such as the LI-COR plant canopy analyser, but such instruments generally give biased estimates. Consequently, conversion factors are required to convert output from the photometer to the actual leaf area index (LAI). Foliar biomass was estimated in a 52-year-old Douglas fir (Pseudotsuga menziesii) stand at Shawnigan in British Columbia, Canada, which had been treated with 3 levels of thinning and 3 levels of fertilizer 28 years previously. The 4 treatment extremes (no thinning or fertilizing, no thinning and heavy fertilizing (448 kg N/ha as urea), heavy thinning (to 1/3 basal area) and no fertilizing, and heavy thinning and heavy fertilizing) were sampled for foliage. Projected leaf areas were calculated from these biomass samples using specific leaf areas derived in a previous biomass sampling. Total one-sided leaf area was then computed by dividing the projected leaf areas by 0.9 to allow for lateral leaf curvature. In addition, LAI-2000 readings were taken in the same plots and then factors were derived to convert LAI-2000 readings to total one-sided LAI. These conversion factors were found to vary strongly with quadratic mean diameter, stand density, mean diameter at breast height, mean height and stand basal area. The effect of live crown height was minimal. These should allow the prediction of the conversion factor based on 2 or 3 of these highly correlated factors.

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12. Beddows, D. 2002. Levels-of-growing-stock cooperative study in Douglas-fir: Report No. 16 - Sayward Forest and Shawnigan Lake. Pacific-Forestry-Centre, Canadian-Forest-Service Information-Report BC-X-393. viii + 67 p.

Keywords: thinning

growth

tree morphology

Abstract: Results from the two levels-of-growing-stock installations at Sayward Forest and Shawnigan Lake on Vancouver Island, British Columbia, Canada, are summarized. Volume growth at both the site-III Sayward Forest installation to age 51 and the site-IV Shawnigan Lake installation to age 52 has been strongly related to level of growing stock. Basal area growth followed a similar, though weaker, trend. Thinning has affected stand development through tree size distribution and live crown development. Periodic annual increments in volume at both installations are still two to three times the mean annual increment, indicating the potential for productivity gains as the treated stands age. Results to date from both installations are similar to results from other cooperative installations, generally differing from the more productive sites only in the rate and degree of response associated with a lower site quality.

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13. Bettinger, P., K.A. Bettinger and K. Boston. 1998. Correlation among spatial and non-spatial variables describing a cut-to-length thinning site in the Pacific Northwest, USA. Forest-Ecology-and-Management 104(1/3): 139-149.

Keywords: thinning

commercial thinning

tree/stand health

Abstract: Variables describing the pre- and post-logging conditions of a thinning site in 47-yr-old naturally regenerated stand of second-growth Douglas fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) in western Oregon, were examined for correlation, and subsequently used to develop models to estimate residual stand damage levels. A cut-to-length harvesting system was utilized to perform the thinning operation, which used a single-grip harvester and a forwarder, and marked logging trails. Several of the variables were measured in an intensive field survey; other variables were developed using geographic information system (GIS) processes. An analysis of correlations among the site variables showed several obvious, and a few interesting, results that describe the operation. Most of the variables provided negative, or inconclusive, assistance in describing the variation in stand damage levels. Only one variable, the number of original trees/hectare, was significantly correlated with residual stand damage levels, and was represented in the models that were developed to estimate residual stand damage levels. The resulting models are of limited practical value, however, since they explain little of the variability in damage levels. Most of the variation in residual stand damage levels may well be explained by random chance, operator error, other unmeasured operational variables associated with this harvesting system, or interactions among variables. The main conclusion from the study is that although both spatial and non-spatial data were utilized in describing the logging operation and in developing models to estimate stand damage levels, the importance of using spatial data was inconclusive.

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14. Bettinger, P. and L.D. Kellogg. 1993. Residual stand damage from cut-to-length thinning of second-growth timber in the Cascade Range of western Oregon. Forest-Products-Journal 43(11/12): 59-64.

Keywords: thinning

commercial thinning

tree/stand health

Abstract: Residual stand damage was measured on 25% of an area that had been thinned with a cut-to-length logging system. Total damage (scar area) per acre was less than in any similar study in the Pacific Northwest, although 39.8% of the residual trees sustained some damage. Only 0.8% of the trees, however, sustained significant damage. Western hemlock (Tsuga heterophylla) was more susceptible to damage than Douglas fir (Pseudotsuga menziesii). Most of the damage occurred within 15 feet of a trail centreline and originated within 3 feet of the groundline. Early summer logging may have resulted in more damaged trees than might occur during other seasons. Future volume loss due to decay is likely to be minimal because a low percentage of scars were considered vulnerable to wood-decaying fungi.

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15. Binkley, D. 1984. Importance of size-density relationships in mixed stands of Douglas-fir and red alder. Forest-Ecology-and-Management 9(2): 81-85.

Keywords: thinning

growth

tree/stand health

Abstract: Pairs of Douglas-fir, and Douglas-fir and red alder (Alnus rubra) stands were examined at four locations (in Oregon, Washington and British Columbia) for patterns in average tree size as a function of stand density. On fertile sites, the mixed stands experienced higher mortality than the pure conifer stands. On infertile sites, the pure conifer stands were well below the maximum tree size and density relationship compared to fertile sites or mixed stands, suggesting under-utilized site resources were available for nitrogen-fixing alder.

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16. Binkley, D. and P. Reid. 1984. Long-term responses of stem growth and leaf area to thinning and fertilization in a Douglas-fir plantation. Canadian-Journal-of-Forest-Research 14(5): 656-660.

Keywords: fertilization

thinning

tree morphology

carbon allocation

growth

Abstract: Replicated thinning and nitrogen fertilization plots in a 53-year-old plantation in Washington State were examined for repsonses in stem growth, leaf area, and stem growth per unit leaf area. Although measurements occurred 20-30 yr after plot installation, substantial effects from the various treatments were still present. Thinning reduced leaf area of the stands but increased stem growth per unit leaf area, resulting in little difference in stem growth per ha over the 5-yr measurement period (1977-81). Fertilization increased both stand leaf area and stem growth per unit leaf area, and more than doubled 5-yr stem growth per ha. Consideration of the role of leaf area and stem growth per unit leaf area in determining stand treatment responses may account for much of the variation found among replicates of treatments or between studies on different sites.

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17. Bodner, J. 1984. Effect of thinning and fertilization on wood properties and intra-ring characteristics in young Douglas-fir. Holzforschung-und-Holzverwertung 36(1): 5-11.

Keywords: fertilization

thinning

wood quality

Abstract: Studies were made on samples from a total of 21 trees (felled in 1982) from 42-yr-old control and thinned/[N] fertilizer-treated stands near Sweet Home, Oregon, and a 48-yr-old thinned stand near Corvallis. Wood properties, studied between and within treatments, included ring density (analysed by X-ray densitometry), earlywood and latewood density, min. earlywood density, max. latewood density, and ring width. There was n.s.d. in av. wood density between treatments. There were significant between-treatment differences in MOE and MOR. Heavy thinning (during the juvenile wood formation phase) reduced latewood fibre length by 26.5%. Min. earlywood density and max. latewood density were the most important components of ring density.

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18. Brandeis, T.J., M. Newton and E.C. Cole. 2001. Underplanted conifer seedling survival and growth in thinned Douglas-fir stands. Canadian-Journal-of-Forest-Research 31(2): 302-312.

Keywords: planting operations

thinning

commercial thinning

site preparation

chemical preparation

release treatments

chemical release

growth

tree/stand health

regeneration

Abstract: In a multilevel study conducted at the Oregon State University's McDonald-Dunn Research Forest, Oregon, USA, to determine limits to underplanted conifer seedling growth, Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), western redcedar (Thuja plicata) and western hemlock (Tsuga heterophylla) seedlings were planted in January 1993 beneath second-growth Douglas-fir stands that had been thinned in 1992 to basal areas ranging from 16 to 31 m2/ha. Understorey vegetation was treated with a broadcast herbicide (glyphosate + imazapyr) application prior to thinning, a directed release herbicide (glyphosate, plus triclopyr for tolerant woody stems) application 2 years later, or no treatment beyond harvest disturbance. Residual overstorey density was negatively correlated with percent survival for all four species. Broadcast herbicide application improved survival of grand fir and western hemlock. Western redcedar, grand fir and western hemlock stem volumes were inversely related to overstorey tree density and this effect increased over time. There was a strong indication that this was also the case for Douglas-fir. Reduction of competing understorey vegetation resulted in larger fourth-year stem volumes in grand fir and western hemlock.

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19. Brandeis, T.J., M. Newton and E.C. Cole. 2002. Biotic injuries on conifer seedlings planted in forest understory environments. New Forests 24:1-14.

Keywords: planting operations

site preparation

chemical preparation

release treatments

chemical release

thinning

tree/stand protection

growth

tree/stand health

Abstract: The effects of partial overstorey retention, understorey vegetation management, and protective Vexar(R) tubing on the frequency and severity of biotic injuries in a two-storied stand underplanted with western redcedar (Thuja plicata), Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), and western hemlock (Tsuga heterophylla) were investigated. The most prevalent source of damage was browsing by black-tailed deer (Odocoileus hemionis columbiana); deer browsed over 74% of Douglas-fir and over 36% of western redcedar seedlings one or more times over the four years of this study. Neither the spatial pattern of thinning (even or uneven) nor the density of residual overstorey affected browsing frequency. Spraying subplots may have slightly increased browsing frequency, but the resulting reduction of the adjacent understorey vegetation increased the volume of all seedlings by 13%, whether or not they were browsed. Vexar(R) tubing did not substantially affect seedling survival, browsing damage frequency, or fourth-year volume. Greater levels of overstorey retention reduced frequency of second flushing. Chafing by deer and girdling by rodents and other small mammals began once seedlings surpassed 1 m in height. Essentially all grand fir seedlings exhibited a foliar fungus infection.

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20. Brix, H. 1984. Effects of thinning and nitrogen fertilization on growth of Douglas-fir: relative contribution of foliage quantity and efficiency. Canadian-Journal-of-Forest-Research 13(1): 167-175.

Keywords: fertilization

thinning

growth

carbon allocation

tree morphology

Abstract: [See FA 43, 1948, 3839] On Vancouver Island, aboveground biomass and annual production over 7 yr was studied in relation to thinning and nitrogen fertilization at 24 yr old. Biomass yield of both treatments increased during the first 3-4 yr then decreased for fertilization but not with thinning. Treatments doubled biomass production of individual trees over the study period when applied separately and quadrupled it when combined. Annual biomass production per unit of foliage (E) increased during the first 3-4 yr, but was at or below control level after 7 yr. E accounted for 20, 37, and 27% of the stemwood dry matter response to thinning, fertilization and the combined treatments, respectively; the remainder was attributed to an increase in foliage biomass. Thinning, but not fertilization, influenced distribution of radial growth along the stem, increasing growth only below the top one-third of the stem. This pattern was related to crown development.

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21. Brix, H. 1993. Fertilization and thinning effect on a Douglas-fir ecosystem at Shawnigan Lake: a synthesis of project results. B.C. Ministry of Forests FRDA-Report 196. X + 64 p.

Keywords: fertilization

thinning

growth

tree morphology

tree/stand health

carbon allocation

wood quality

tree physiology

photosynthesis

economics

Abstract: Treatments were initiated in 1970-71 in a 24-year-old Douglas fir (Pseudotsuga menziesii) near Shawnigan Lake, Vancouver Island, British Columbia, to determine the effects of 3 intensities of thinning (removing none, one-third and two-thirds of basal area) and 3 levels of urea fertilizer (0, 224 and 448 kg N/ha) on the growth and biology of the trees. Subsidiary experiments were established during 1972-87 to examine the effects of high doses of urea (672-1344 kg N/ha), ammonium nitrate as an N source instead of urea, understorey response to thinning and fertilizer, and responses to P and S fertilizer.

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22. Brix, H. and A.K. Mitchell. 1983. Thinning and nitrogen fertilization effects on sapwood development and relationships of foliage quantity to sapwood area and basal area in Douglas-fir. Canadian-Journal-of-Forest-Research 13(3): 384-389.

Keywords: fertilization

thinning

tree morphology

tree physiology

Abstract: A 24-yr-old stand in British Columbia was treated in 1971-72 with various intensities and combinations of N fertilization and thinning. For 5-9 yr after treatments, trees were sampled to determine effects on foliage quantity and sapwood characteristics at varying stem ht. together with their relationships. Sapwood width remained relatively constant up the stem where heartwood was present, but the number of annual rings it contained decreased with ht. The sapwood width at b.h. increased with stem diam.; treatments had little effect on % sapwood at b.h. The ratio of foliage mass to sapwood cross-sectional area changed for different portions of the crown and was lower when based on sapwood area at b.h. than at base of live crown. Significant linear relationships of foliage mass and area to sapwood area at b.h. were found, but relationships of foliage to b.a. were just as close for all treatments; treatments significantly affected these relationships with control trees having the lowest regression slopes.

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23. Brix, H. and A.K. Mitchell. 1986. Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand. Canadian-Journal-of-Forest-Research 16(6): 1334-1338.

Keywords: thinning

fertilization

soil properties

tree physiology

Abstract: Soil and tree water potentials were studied for 10 yr in a Douglas fir stand near Shawnigan Lake, British Columbia that was treated when 24 yr old with heavy thinning (removing superscript 2/3 of b.a.) and/or fertilization with 448 kg N/ha as urea. Control plots were not thinned or fertilized. Throughout the 10 yr, thinning increased soil water potential during the dry summer periods (July-early Oct.) by as much as 1 MPa. The effect of fertilization on soil water potential was slight and nonsignificant, and only apparent towards the end of the study in spite of large increases in leaf area (50% after 7 yr). Fertilization increased water use efficiency. The favourable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understorey in a thinned and fertilized plot did not affect soil or shoot water potential.

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24. Buermeyer, K.R. and C.A. Harrington. 2002. Fate of overstory trees and patterns of regeneration 12 years after clearcutting with reserve trees in Southwest Washington. Western-Journal-of-Applied-Forestry 17(2): 78-85.

Keywords: thinning

regeneration

tree/stand health

Abstract: Changes in management objectives for some forestlands in the Pacific Northwest have spurred interest in the creation of multistoried stands and the use of natural regeneration systems, but data on such systems are lacking. We assessed the status of the overstory trees and the regeneration 12 yr after a clearcut harvest with reserve trees in an even-aged, 145-yr-old Douglas-fir stand on a moderately productive site (site class 3) in southwest Washington. The 15 ha harvest unit was superimposed over two areas differentially thinned 15 and 34 yr before clearcutting. The clearcut harvest retained 18 trees/ha with a mean diameter of 63 cm. The reserved overstory trees had a 93% survival rate after 12 yr; most dead trees had been windthrown. Diameter growth for the reserved trees averaged 3.3 cm and was greatest during the most recent 3 yr period, which also had the highest growing-season precipitation. In a 1 ha mapped area, there were 5,854 seedlings/ha, and more than 99% of the regeneration was Douglas-fir. Most seedlings were less than 2 m tall. Seedling density was somewhat clumped (value of 2.1 for Pielou's index of nonrandomness), but 79% of randomly located 4.04 m2 (mil-acre) plots and 98% of 5x5 m grid cells had at least one conifer seedling. There was no obvious pattern of regeneration based on direction from the reserved trees, but both seedling density and seedling size within the drip lines of reserved tree crowns were less than in the rest of the area. The number of seedlings was similar on the two halves of the plot corresponding to the original thinning blocks, but seedling size and age differed. In the half of the study plot that had been twice lightly thinned, only 14% of the seedlings were >0.5 m tall; however, 41% of the seedlings were >0.5 m in the block that had been thinned more heavily. There was no difference between the thinning blocks in the ages of seedlings <less or =>0.5 m tall (mean age of 5 yr). This example of clearcutting with reserve trees resulted in reasonable survival of the overstory trees and adequate stocking but slow growth rates in the naturally regenerated Douglas-fir. Heavier thinning before harvest was associated with more advance regeneration, more shrub cover, and less windthrow of the reserved trees than in the more lightly thinned block. If an abundance of tree species other than Douglas-fir was desired on this site, interplanting would be required.

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25. Busing, R.T. and S.L. Garman. 2002. Promoting old-growth characteristics and long-term wood production in Douglas-fir forests. Forest-Ecology-and-Management 160(1/3): 161-175.

Keywords: thinning

yield

wood quality

Abstract: Trade-offs among wood production, wood quality and ecological characteristics in the management of harvested forest stands are explored through model simulation of various silvicultural regimes. Long-term production of merchantable wood, production of various types of high-quality wood, and the level of certain quantitative ecological indicators are projected for coniferous forests of Pacific Northwestern USA. The set of ecological indicators used is based on the species composition and physical structure of old, unlogged forest stands. Simulations are performed with an ecological model of forest stand dynamics that tracks the fate of live and dead trees. Short rotations (<50 years) produce the least amount of high-quality wood over the multi-century simulation period. They also fail to generate ecological attributes resembling those of old forest stands. Production of high-quality wood is moderate to high under all rotations of 80 years or more; however, most ecological indicators require longer rotations unless alternatives to clear felling are applied. Alternatives examined include retention of 15% cover of live tree canopy at each harvest in combination with artificial thinning between harvests. Thinning from below can expedite the development of large live and dead trees, and canopy height diversity without greatly diminishing wood quantity or quality. Proportional thinning retains understorey stems, thereby expediting the recruitment of shade-tolerant trees. A possible drawback to thinning, particularly proportional thinning, is the diminished production of clean-bole wood at rotations of 150 and 260 years. It is concluded that most wood quantity, wood quality and ecological objectives can be met with long rotations (approximately 260 years). Certain objectives can be met with shorter rotations (80-150 years) when treatments of thinning and canopy tree retention are applied.

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26. Carter, R. and R. Scagel. 1989. The effects of stand density and fertilization on stand development in immature coastal Douglas-fir. B.C. Ministry of Forests FRDA-Report 094. i + 15 p.

Keywords: fertilization

thinning

growth

tree morphology

Abstract: The effects of urea fertilizer were studied in Pseudotsuga menziesii stands spaced to 500, 750 and 1000 stems/ha in coastal British Columbia.

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27. Chen, J.M. and T.A. Black. 1992. Foliage area and architecture of plant canopies from sunfleck size distributions. Agricultural-and-Forest-Meteorology 60(3/4): 249-266.

Keywords: thinning

pruning

tree morphology

Abstract: A Poisson model is developed to describe sunfleck or gap size distributions beneath clumped plant canopies. This model is based on the assumption that foliage clumps are randomly distributed in space and foliage elements are randomly distributed within each clump. Using this model, the foliage clumping index, leaf area index (L), clump area index, element area index in each clump, and element and clump widths were successfully derived for two artificial canopies and a thinned and pruned Douglas-fir (Pseudotsuga menziesii) forest stand. It is shown that existing theories for deriving L from measurements of canopy gap fraction have limitations, and use of canopy architectural information derived from canopy gap size distribution can substantially improve the technique for indirectly measuring L of plant canopies.

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28. Christiansen, E.C. and S.G. Pickford. 1991. Natural abatement of fire hazard in Douglas-fir blowdown and thinning fuelbeds. Northwest-Science 65(4): 141-148.

Keywords: thinning

precommercial thinning

tree/stand health

Abstract: The changes over time in fuelbed loading and depth in precommercially thinned and windthrown low altitude stands of Douglas fir (Pseudotsuga menziesii) were investigated in the Bull Run Watershed, Oregon, using standard fuel inventory techniques. Non-linear least squares regressions were fitted to the resulting data. Slash from precommercial thinning lost half of its original loading and depth within 2 yr. No foliage was retained on twigs and branches after 1 yr. Changes in fuels from windthrown trees were similar to those in slash, except that more material was present initially. Fine fuels (<3 inches in diameter) decreased to background levels within 2-4 yr, but large fuels persisted for longer. Sound logs became rotten after about 80 yr. The study confirmed that the fire hazard after precommercial thinning slash and wind throw was abated after 3 yr.

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29. Cole, D.W., M.L. Rinehart, D.G. Briggs, C.L. Henry and F. Mecifi. 1984. Response of Douglas fir to sludge application: volume growth and specific gravity. In Proceedings of the Technical Association of the Pulp and Paper Industry 1984 Research and Development Conference, Appleton, Wisconsin, September 30-October 3. pp. 77-84.

Keywords: fertilization

thinning

growth

wood quality

Abstract: In 1977 and 1980 municipal sludge was applied to a 60-yr-old lowland Douglas fir stand in Washington State. Application procedures and rates and suitable sites for treatment are described. There was a 6 yr av. diam. growth response of 93% in unthinned and 48% in thinned stands treated with 142 t/ha sludge and a vol. growth response of 53 and 42%, respectively. The accelerated rate of growth has not shown signs of decreasing since treatment. Relative density of sludge-grown wood was 10-15% less than that of untreated wood, but within the range for Douglas fir grown on higher land. This is thought to be a result of the change in forest site produced by the sludge treatment.

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30. Collier, R.L. and E.C. Turnblom. 2001. Epicormic branching on pruned coastal Douglas-fir. Western-Journal-of-Applied-Forestry 16(2): 80-86.

Keywords: pruning

thinning

wood quality

tree morphology

Abstract: The Stand Management Cooperative (SMC 1998) at the University of Washington, USA, conducted live crown reduction experiments in the Pacific Northwest regions of the USA, to better understand the dynamics of the response of coastal Douglas fir (Pseudotsuga menziesii) to pruning. A detailed report on how frequently epicormic branches occur, where they occur on the bole, whether or not their occurrence is related to stand density or the amount of crown removed, and how epicormic sprouting may affect log grade, is presented. The experiments include fifty-six 0.08 ha pruning plot in 18 installations in British Columbia, Oregon and Washington. As part of the monitoring process, a subset of 38 plots in 12 installations was examined for the occurrence and size of epicormic branches 4 years after the initial pruning treatments. Results showed that epicormic branching was most severe on the south and west sides of trees. When epicormic branching was severe, sprouts occurred both at nodes (or whorls) and along internodes. Less severe or moderate sprouting tended to originate mainly in nodes. The risk of epicormic branching is minimal as long as the pruning treatment does not reduce the live crown by more than 40% and the stand has 500 or more stems/ha. The highest risk of epicormic branching was found to be when the live crown is reduced by more than 40%, and the stand carries less than 500 stems/ha.

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31. Cruickshank, M.G., D.J. Morrison and Z.K. Punja. 1997. Incidence of Armillaria species in precommercial thinning stumps and spread of Armillaria ostoyae to adjacent Douglas-fir trees. Canadian-Journal-of-Forest-Research 27(4): 481-490.

Keywords: thinning

precommercial thinning

tree/stand health

Abstract: The frequency of Armillaria species in precommercial thinning stumps and the interaction at root contacts between Douglas fir (Pseudotsuga menziesii) crop trees and stumps colonized by A. ostoyae were investigated at sites in four biogeoclimatic zones along a transect from the coast through the southern interior of British Columbia. The frequency of stumps colonized by A. ostoyae and A. sinapina varied among lower, mid, and upper slope transects. On coastal sites, A. sinapina dominated fresh hygrotopes and A. ostoyae dominated slightly dry hygrotopes, and the frequency of both fungi was low on moist hygrotopes. On interior sites, A. ostoyae was found over all hygrotopes, but with lower frequency on the driest sites. The distribution of the two Armillaria species on sites is apparently determined by anoxia associated with periodic soil saturation, by drying of the soil, and by host response limiting spread of pathogenic species. At root contacts between colonized stump roots and crop tree roots, transfer and infection by A. ostoyae occurred more frequently in moist biogeoclimatic zones than dry ones. Lesion size on crop tree roots was related to inoculum volume at some sites and to stump root diameter at others. The percentage of lesions on roots at which crop trees formed callus was associated with tree bole volume. The results indicate that there will be crop tree mortality following precommercial thinning, especially where inoculum levels are high in the Interior Cedar-Hemlock and Interior Douglas fir biogeoclimatic zones.

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32. Curtis, R.O. 1987. Levels-of-growing-stock cooperative study in Douglas-fir: Report No. 9 - some comparisons of DFSIM estimates with growth in the levels-of-growing stock study. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Paper PNW-RP-376. 34 p.

Keywords: thinning

commercial thinning

growth

tree/stand health
computer modeling

Abstract: Initial stand statistics for the 9 levels-of-growing-stock (LOGS) study installations in Oregon and Washington, USA, and Vancouver Island, British Columbia, Canada, were projected by the Douglas fir (Pseudotsuga menziesii) stand simulation program (DFSIM) over the available periods of observation. Thinnings were simulated by use of observed top height trends, actual residual basal areas, and actual ratios of cut tree diameters to stand diameter before cutting (d/D). Estimates were compared with observed gross and net volumes and basal area growth, net change in quadratic mean diameter, and change in number of trees. Although the LOGS installations included regimes quite different from those in most of the data used to construct DFSIM, overall agreement was reasonably good. Results indicated some density-related bias in the thinned stands and a need for revision in the method used to control the maximum density in the DFSIM program and in the associated mortality estimates.

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33. Curtis, R.O., G.W. Clendenen and D.J. DeMars. 1981. A new stand simulator for coast Douglas-fir: DFSIM user's guide. Pacific-Northwest-Forest-and-Range-Experiment-Station,-USDA-Forest-Service General-Technical-Report PNW-GTR-128. ii + 79 p.

Keywords: planting operations

thinning

precommercial thinning

commercial thinning

fertilization

yield

computer modeling

Abstract: A description of a computer program, written in FORTRAN IV, for simulating managed stands. The program has been developed from remeasured plot data contributed by many organizations in the Pacific Northwest USA. It can produce yield tables which include estimates of effects of initial spacing, precommercial and commercial thinning and addition of N fertilizer. Topics discussed include program limitation and potential for further development. Appendices include operating instructions and notes on testing. The program is available from the authors on request.

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34. Curtis, R.O. and D.D. Marshall. 1986. Levels-of-growing-stock cooperative study in Douglas-fir. Report no. 8 - The LOGS study: twenty-year results. Pacific Northwest Research Station, USDA Forest Service Research-Paper PNW-RP-356. v + 113 p.

Keywords: thinning

commercial thinning

growth

Abstract: A further report in a series on 9 study areas in Oregon, Washington and British Columbia. The programme aimed to determine relations between growing stock and vol., b.a. and diam. growth for 8 thinning regimes. Results presented are mainly from 5 site class II installations. Growth was strongly related to growing stock. Thinning treatments produced marked differences in volume distribution by tree sizes. There were considerable unexplained differences in productivity between installations, beyond those attributable to site quality. During the 4th treatment period (32-42 yr old in site class II sites) c.a.i. was approx. twice m.a.i. An evaluation is given of the LOGS study design.

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35. Curtis, R.O. and D.D. Marshall. 2002. Levels-of-growing-stock cooperative study in Douglas-fir: report no. 14 - Stampede Creek: 30-year results. Pacific-Northwest-Research-Station,-USDA-Forest-Service Research-Paper PNW-RP-543. xi + 77 p.

Keywords: thinning

commercial thinning

growth

yield

tree morphology

tree/stand health

Abstract: Results of the Stampede Creek installation of the levels-of-growing-stock (LOGS) study in Douglas-fir (Pseudotsuga menziesii) are summarized. To age 63 (planned completion of 60 feet of height growth), volume growth on the site III natural stand has been strongly related to level of growing stock, but basal area growth-growing stock relations were considerably weaker. Marked differences in tree size distributions have resulted from thinning. Periodic annual volume increments at age 63 are two to three times greater than mean annual increment; this stand is still far from culmination. Results for this southwest Oregon installation are generally similar to those reported from other LOGS installations, although development has been slower than on the site II installations that make up the majority of the series.

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36. Curtis, R.O., D.D. Marshall and J.F. Bell. 1997. LOGS: a pioneering example of silvicultural research in coast Douglas-fir. Journal-of-Forestry 95(7): 19-25.

Keywords: thinning

commercial thinning

growth

yield

Abstract: A regional levels-of-growing-stock (LOGS) study of young Douglas fir (Pseudotsuga menziesii) stands in western Oregon and western Washington, USA and Vancouver Island, British Columbia, Canada, was conducted between 1961 and 1970. The objective was to determine how the amount of growing stock retained in repeatedly thinned stands of P. menziesii affects cumulative wood production, tree size and growth:growing stock ratios. Nine LOGS installations were established during the study period, each consisting of 27 one-fifth acre plots, with 8 thinning treatments (and controls). All plots received initial calibration thinning. After the first 10 feet of height growth and at intervals of 10 feet thereafter, 5 subsequent thinning treatments were made. As of 1994, all installations on site class II, and most installations on site classes III and IV had completed the planned thinning sequence over 60 ft of height growth. Periodic annual increment of both basal area and volume was clearly related to basal area of growing stock and several measures of density. Thinning accelerated diameter growth, and diameter and volume distributions differed greatly among treatments. Mean annual increment and periodic annual increment showed no sign of approach to culmination in either total or merchantable cubic volume. Cumulative volume production (live stand plus thinning) of the controls exceeded all thinning treatments to date when measured in total cubic volume of all trees, although when volume was measured in merchantable cubic feet several thinning treatments exceeded net volume production of the controls. A discussion of the results includes: a comparison with other thinning studies; an analysis of application of the Langsaeter hypothesis (that the same cubic volume production could be obtained over a wide range of stand densities); growth trends and rotations; thinning gains; non-timber values; and critical analysis of the study design. The continuing value of the demonstration stands is discussed.

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37. Curtis, R.O., D.D. Marshall and D.S. DeBell. 2004. Silvicultural options for young-growth Douglas-fir forests: the Capitol Forest study - establishment and first results. Pacific Northwest-Research-Station,-USDA-Forest-Service General-Technical-Report PNW-GTR-598. xi + 110 p.

Keywords: thinning

commercial thinning

economics

soil properties

Abstract: This report describes the origin, design, establishment and measurement procedures and first results of a large long term cooperative study comparing a number of widely different silvicultural regimes applied to young-growth Douglas-fir (Pseudotsuga menziesii) stands managed for multiple objectives. Regimes consist of (1) conventional clear felling followed by intermediate thinning; (2) retention of reserve trees to create a two-aged stand; (3) small patch cuts dispersed within a thinned matrix, repeated at approximately 15-year intervals to create a mosaic of age classes; (4) group selection within a thinned matrix on an approximate 15-year cycle; (5) continued thinning on an extended rotation; and (6) an untreated control. Each of these regimes is on operation-size units (approximately 30 to 70 acres each). A LIDAR system was used to scan the surface of the 2 miles2 that encompass the Blue Ridge study site on the Capitol State Forest, near Olympia, Washington, USA